This invention relates to a method of directly determining setting values for the application point of regulation in a regulated draw frame for slivers. The control system of the draw frame in which the extent of draft of the sliver may be set has at least one preliminary control system for changing the draft of the sliver. Based on the drafted sliver, a number of quality-characterizing measured values, such as CV values may be sensed and utilized for formulating a function whose minimum represents an optimum application point of regulation for the control of the draw frame. The optimized application point of regulation may be determined in a pre-operational test run or a setting run of the draw frame.
The application point of regulation is an important setting magnitude in a draw frame to produce slivers with a high sliver uniformity, that is, with a small CV value.
In a known system, during a pre-operational setting run, the sliver is drafted between the mid rolls and the output rolls of the draw unit and is withdrawn by calender rolls which are adjoined by a measuring device for the CV value of the drafted sliver. In the pre-operational setting run a plurality of CV values are determined which represent a quality-characterizing magnitude for the drafted sliver. Based on such measured values, a function is formulated whose minimum value corresponds to a value which promises to be the best adaptation of the regulation actual sliver. The plurality of measured values which are plotted and based on which the function is formulated, are in each instance measured for a different setting value of the regulation. Thus, for the definition of the function to be evaluated, each incremental value of an incrementally changing parameter, for example, the application point of regulation of the xe2x80x9celectronic memoryxe2x80x9d, has to be associated with one of the measured values. It is a disadvantage of this system that the quality of the un-drafted sliver (input quality) introduced into the draw unit cannot be taken into consideration. It is a further drawback that only one certain CV value is considered.
It is an object of the invention to provide an improved method of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, ameliorates the determination and setting of the optimal application point of regulation at the regulating system of a draw unit.
These objects and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of directly determining setting values for an application point of regulation in a draw unit for drafting sliver, includes the following steps: obtaining a plurality of measured values of a quality-characterizing magnitude, such as a CV value, of the drafted sliver portion; utilizing the measured values for formulating a function having a minimum constituting an optimal application point of regulation for controlling the draw unit; determining the optimal application point of regulation in a pre-operational run of the draw unit; obtaining several measured values of a quality-characterizing magnitude based on an un-drafted sliver portion and determining the function between the quality-characterizing magnitudes and application points of regulation from measured values at the un-drafted silver portion and at the drafted sliver portion.
The optimal application point of regulation (optimal dead period or delay) is determined by the draw frame itself by using the steps according to the invention. Based on the CV values of the sliver measured on line, the draw frame control system determines the optimal application point of regulation, that is, the machine optimizes itself. By utilizing the CV values of both the un-drafted and the drafted sliver the application point of regulation is determined more accurately, since effects of the incoming sliver too, such as those caused by thickness changes, are taken into consideration. Further, a more rapid determination of the application point of regulation is feasible.